1. Field of the Invention
The present invention relates to a fluorescent lamp lighting device for lighting a fluorescent light bulb by using an electronic lighting circuit.
2. Description of the Related Art
In recent years, as fluorescent lamp lighting devices, inverter-type electronic lighting devices have been commonly used in order to save energy. In particular, in fluorescent lamps incorporated in a lighting device, which is an energy-saving light source, in order to achieve higher-efficiency of a lamp, inverter-type electronic lighting circuits are becoming increasingly used.
Japanese Unexamined Patent Application Publication No. 2001-357989 discloses a known fluorescent lamp. That is, ordinary fluorescent lamps are configured as shown in FIG. 3. A circuit substrate 20 on which an electronic lighting circuit 3 is formed is arranged between a base 6 arranged at the end portion of a resin case 5 and a fluorescent light bulb 2, and electronic components for insertion mounting are mounted on the circuit substrate 20.
Furthermore, a known fluorescent lamp has an electronic lighting circuit shown in FIG. 2. The configuration of the circuit will now be described below with reference to FIG. 2.
The electronic lighting circuit 3 includes a fluorescent light bulb 2, a power source 13, and an inverter circuit section 14. A terminal “a” of one of electrode filaments 7 contained in the fluorescent light bulb 2 is directly connected to the inverter circuit section 14. Furthermore, a terminal a′ of the other electrode filament 8 contained in the fluorescent light bulb 2 is connected in series to the inverter circuit section 14 via an inductance element 15 for controlling electrical current. A capacitor 18 and a positive characteristic thermistor (hereinafter referred to as a “PTC thermistor”) 19 are connected in parallel between a terminal b of the electrode filament 7 and the terminal b′ of the electrode filament 8. Furthermore, a negative characteristic thermistor (hereinafter referred to as an “NTC thermistor”) 16 is connected between the terminals a and b of the electrode filament 7, and an NTC thermistor 17 is connected between the terminals a′ and b′ of the electrode filament 8.
On the surface of the fluorescent lamp that faces the base of the circuit substrate, comparatively large electronic components for insertion mounting, such as a smoothing capacitor, a resonance capacitor, a resonance coil, a PTC thermistor, and an NTC thermistor, are mounted, and the components are in close proximity with each other.
Here, in a case where, after the fluorescent lamp is temporarily lit normally, the power supply is switched off, the cooling speed of the NTC thermistor differs according to how close the NTC thermistor is to the other components.
Furthermore, when a component which is close to an NTC thermistor is a self-heating component, such as a PTC thermistor, it becomes difficult for the NTC thermistor to cool due to the self-heating, and the off time required to maintain the pre-heating efficiency of the filament, that is, the reset time, becomes long.
Therefore, at the restarting time, since it is difficult to ensure pre-heating current which flows through the electrode filament, there is a risk in that the number of on-off operations of the lamp may be decreased due to insufficient pre-heating.